It has been known since Mitchell and Kingbury's calculations of 1905 that the pivoted pad slider bearing is a desirable kind of bearing with excellent friction and film stability characteristics. The pivoted pad adjusts the angle of convergence of the oil wedge film between the pad surface and a surface sliding with respect to the pad surface so that the convergence angle of the wedge film adjusts to establish a balance of oil pressure force moments about the pad. This pivoting permits the pad to adjust the wedge angle to optimize friction and oil film thickness over a wide range of operating conditions. Pivoted pads have been in service for more than 70 years. However, the load bearing capacity of pivoted pad slider bearings is limited because of deformations of the pads and limitations of the support structure. It is the purpose of the present invention to provide an elastomeric support structure for a pivoted pad which is extremely strong in compression, pivots freely, and is particularly desirable for applications of a pivoted pad slider involving fluctuating forces and squeeze film effects.
Attempts to produce a pad pivot by simply mounting the metal pivoting pad on an elastomeric pad have been made before, and have been relatively unsuccessful. Elastomeric pads, even of materials of small Young's modulus, are very stiff with respect to pivoting since pad compressibility constrains the pivoting. In the present elastomeric pad design this compressibility effect is eliminated because the elastomeric pad contains within itself a small volume of liquid which can transfer volume back and forth as the pad pivots. When this elastomeric pad is fully surrounded structurally (so that bulging is constrained and pad bulk modulus is important with respect to direct compression), a pad support is formed which is strong with respect to direct compression, but quite flexible and free with respect to the small pivoting angles required for a pivoted pad slider support.
This liquid filled elastomeric pad support structure tends to bend the pad into a more convex shape when the bearing pad is loaded. This is not desirable for applications where the bearing load is heavy and steady. However, this bending tendency is useful if the pad is subject to fully reversing loads. In a case where load reversal occurs and a thick oil film is established between the pad and its coacting sliding surface, the deformability of the elastomerically supported pad acts to automatically adjust pad geometry to maximize the importance of the squeeze film effect. This produces thicker oil films than would occur without pad compliance, and consequently reduces friction.